Gun barrels must be kept as clean as possible for reliable operation of the firearm. Use in extreme environments and in combat presents multiple opportunities for dirt and debris to enter the barrel through the muzzle and thereby foul the weapon. This can result in permanent damage to the interior surface of the barrel and/or disabling of the gun. Because gun muzzles heat to very high temperatures during use, particular in semi and fully automatic firing modes, it has not been practical to cover or protect the barrel particularly at the muzzle end.